EP4675648A1

EP4675648A1 - Data cables with coaxial wire reinforced composite for shielding

Info

Publication number: EP4675648A1
Application number: EP24186475.0A
Authority: EP
Inventors: Szymon DUKALA; Pawel Kozak
Original assignee: Aptiv Technologies AG
Current assignee: Aptiv Technologies AG
Priority date: 2024-07-04
Filing date: 2024-07-04
Publication date: 2026-01-07

Abstract

A coaxial data cable (30) comprises a core of conductor wires (1), and a shielding layer arranged around the conductor wires, made of an extruded shielding composite comprising a matrix (3) and a reinforcement by continuous wires (2). The continuous wires (2) preferably extend substantially parallel to each other.

Description

1. Field of the invention

The present invention relates to a shielded data cable for data transmission, such as signal cables.

2. Technical background

In many fields of applications, electrical cables and connections need to be electromagnetically shielded. In particular in the automotive industry signal transmission lines are required to handle increasingly high data transmission speeds. Due to the speeds involved, shielding of the connectors and cables is an essential need to avoid possible interferences. Due to the large demand for electrical components, e.g., in the field of automotive applications, such components must be efficiently and inexpensively producible; however, they still must fulfill high quality standards.
To produce shielded data cables known solutions use a three-step process, whereby the shielding is applied in a braiding step. Such braiding is typically made with Al PET or aluminum foil and taping by Al PET or aluminum foil. Braiding the shield on the cables has however several limitations. The linear speed of braiders is slow, which makes the whole step of braiding slow. Additionally, this increases the costs because less cables can be produced when shielding is needed. Furthermore, it has proven to be difficult to provide a crimped termination to the cables when the shielding is braided.
Subject of the present invention is to provide a new data cable which minimizes or eliminates the above-described problems. It is a further object of the invention to provide shielded data cable, which is faster, easier, and less expensive to produce. Additionally, it is an object of the invention to propose a cable for which production steps can easily be automatized. Further, it is an object of the invention to achieve all the mentioned advantages with a cable, which can be easily crimped.

3. Summary of the invention

According to the invention, a coaxial data cable is provided, which comprises a core of conductor wires and a shielding layer arranged around the conductor wires, made of an extruded shielding composite comprising a matrix and a reinforcement by continuous wires, the continuous wires preferably extending substantially parallel to each other. The extruded shielding composite constitutes a whole and replaces the conventional braided screen.
A key aspect of the invention is that a shielding composite is extruded on the core of conductor wires. With the extrusion step, a matrix and reinforcement made of continuous wires together create the electromagnetic shielding function (ESF) required to electromagnetically shield the data. Instead of technically sophisticated, braided, intertwined wires, the ESF is preferably created by the conductive properties of the material of the matrix complemented by parallel wires. Consequently, the usual braiding step to shield the conductor wires is eliminated and replaced by an extrusion step. By extruding the shielding on the core of conductor wires a faster production is possible compared to braiding the shielding layer. Not only is the process of extruding the shielding faster than braiding the shielding but extruding the shielding simultaneously covers the core, thereby reducing the production steps needed to produce the cables, and thus increasing even more the production speed. Additionally extruded shielding facilitates the process of crimping and assembling the connectors. The coaxial data cable according to the invention preferably does not comprise any layer with intersecting wires, in particular no braided layer, more particularly no braided electromagnetic shielding layer.
Another advantage of the data cable according to the invention is that these cables can be used interchangeably with previous data cables, i.e., there are no compatibility issues between new data cables and data cables according to the invention.
The coaxial data cable comprises an insulation layer directly surrounding the core of the conductor wires, the insulation layer being arranged between the core and the shielding layer. An insulation layer of the jacket provides mechanical and environmental protection of the cable, as well as galvanic separation from the rest of the system.
Furthermore, the coaxial data cable can comprise a foil covering the insulation layer, and therefore arranged between insulation layer and shielding layer. This generally helps to obtain the appropriate transfer impedance, which is specified in standards and shows how susceptible the cable is to external noise or EMC emissions.
The coaxial data cable can also be protected from external influences, such as temperature or mechanical impact, by an external jacket arranged on top of the shielding layer.
With the extrusion step, the production process is simplified, and its efficiency is increased with the invention, thereby reducing costs, but at the same time this is not done at the expense of the transmission properties of the cables. In fact, the use of a shielding composite provides the same or an improved shielding and transmission properties when compared to usual braided shielding.
The approach is innovative due to the combination of two different materials with extremely different mechanical properties, but which may have a similar electrical nature which creates a shielding composite. In addition, the solution is based on very simple extrusion technologies and innovative longitudinal application of metal or alloy wires to ensure the required resistivity and shielding of cables.
The material chosen for the matrix of the shielding composite should therefore preferably be electroconductive, with a conductivity of at least 1*10⁵ S/m. More electroconductive matrix material typically enhances the shielding properties. Therefore, material having a conductivity of at least 5*10⁵ S/m, and even more preferably at least 1*10⁶ S/m and most preferably at least 1*10⁷ S/m, can also be chosen, depending on the desired shielding properties. Matrix materials having conductive properties are generally known to the skilled person, example materials for the matrix of the shielding composite are plastic doped with graphene, carbon black or additives causing electrical conductivity, such as Polypropylene with carbon black, PVC with carbon black, PVC with Graphene. Such plastics retain their plastic structure and can be used in an extrusion process. The continuous wires improve shielding properties at low frequencies. and the conductive matrix supports high-frequency shielding by creating conductive path between longitudinal wires. Nevertheless, in some embodiments, also non-electroconductive matrix material can be chosen, such as PP, TPE-S, PVC. Although such embodiments have a limited shielding functionality, they have the advantage of using a regular plastic matrix and offering the possibility of dispensing with an external jacket.
It has been found that the choice of the continuous wires is advantageous in adapting the shielding properties of the shielding composite, and in particular to change the transfer impedance values. On one hand, the dimensions of the wires can e.g., be chosen, whereby thicker wires provide a higher shielding but also tend to make the coaxial cable stiffer. On the other hand, the appropriate material with the necessary conductivity to obtain the desired shielding can be chosen. The selection of matrix materials and wire geometry is always related to the requirements imposed on the cable structure. When using graphene-based materials, it is possible to obtain high shielding properties without electrical conductivity of the matrix material.
To reach the required shielding properties, the continuous wires can have a diameter of 0,1 mm to 1 mm, preferably between 0,1 mm and 0,8 mm, more preferably between 0,2 mm and 0,6 mm.
The material chosen for the continuous wires should preferably have a conductivity of at least 1*10⁶ S/m, more preferably at least 5*10⁶ S/m, even more preferably at least 1*10⁷ S/m and most preferably at least 5*10⁷ S/m. Preferably the conductivity of the wires is chosen higher than the conductivity of the matrix material, as this has an advantageous impact on the shielding properties. It allows to use a less performant matrix for same shielding results.
Typical materials that can be used for the continuous wires of the shielding composite are for example copper CU, alloy copper CuSn or tinplated copper wires, whereby enough wires should be added to the shielding composite to ensure an appropriate electrical conductivity.
At least 4 continuous wires of the shielding layer are preferably arranged symmetrically around the core, which allows the use of simplified methods of connection systems and automation, and which opens new possibilities for designers of plugs and sockets. Symmetrical placement also allows for proper positioning of wires in the process of automatic crimping and making of connection terminals. Depending on the desired shielding properties and the desired resistance, it can be desired to arrange at least 8 or at least 16 continuous wires symmetrically around the core.
Preferably, the diameter of the continuous wires is substantially equal the thickness of the shielding layer. This provides a maximized shielding while requiring minimal matrix material. However, care should be taken that diameter of the wires is not greater than the thickness of the matrix, because in such a case it is difficult to co-extrude the matrix and the surface would have significant surface irregularities that would adversely affect the parameters. It should further be taken into account that very large a diameter of the wires negatively affects the cable's electrical properties.
One important advantage of extruded shielding in comparison with braided shielding is that the ends of the coaxial cables always offer substantially parallel wires at the ends, which are much easier to crimp than braided ends of coaxial cables, such that it is easier to connect the coaxial cable of the invention to connection systems like plugs, connectors, hoses or the like.
To produce a coaxial data cable according to the invention, at least two production steps are required: in a first step a core of conductor wires is provided, in a second step a shielding layer made of a shielding composite is extruded around the core of conductor wires, wherein the shielding composite comprises a matrix and a reinforcement by continuous wires, the continuous wires preferably extending substantially parallel to each other.
Preferred optional method steps include the steps of surrounding the core of conductor wires with an insulation layer before extruding the shielding layer, surrounding the insulation layer with a foil before extruding the shielding layer, and/or extruding an external jacket on the shielding layer.
Because of the parallel continuous wires of the shielding layer, it is further possible to automatize the step of crimping the ends of the coaxial data cable, for implementation of connection systems like plugs, connectors, hoses or the like.

4. Description of the figures

In the following, the figures, showing the state of the art and specific embodiments of the present invention, are briefly described.

Fig. 1 schematically shows the production process of coaxial data cables of the state of the art.
Fig. 2 schematically shows the production process of coaxial cables according to the present invention in comparison with the production process of the state of the art.
Fig. 3 shows a first example embodiment of the coaxial data cable according to the invention.
Fig. 4 shows a second example embodiment of the coaxial data cable according to the invention.
Fig. 5 shows a third example embodiment of the coaxial data cable according to the invention.
Fig. 6 shows a fourth example embodiment of the coaxial data cable according to the invention.

Figure 1 shows a typical production method for coaxial data cables 30 in the state of the art. To produce coaxial cables 30, first an insulation layer is extruded on a core of conductor wires 1. The result of this first production step 110 is an intermediate product, namely an insulated core of conductor wires 10. In a second production step 120, the insulated core of conductor wires 10 is introduced into a braiding machine, where a shield of intertwined wires is braided around the insulated core of conductor wires 10. The result is another intermediate product, namely a shielded core of conductor wires 20. In a third production step 130 after braiding, a protective external jacket is extruded around the shielded core of conductor wires 20. At the end of the manufacturing process a coaxial data cable 30 is obtained. Several problems arise with this manufacturing process. Firstly, the braiding step 120 requires the insulated core of conductor wires 10 to pass from an extrusion machine to a braiding machine. Thereafter, the thus shielded core of conductor wires 20 is passed onto yet another extrusion machine for the last step 130 of manufacturing an external jacket. Secondly, the braiding machines are relatively slow when compared to the speed of extrusion machines because the braiding wires need to be intersected, which also considerably increases the complexity of the machine. The braiding step 120 therefore significantly increases the costs of such coaxial data cables 30. Additionally, because the ends of the coaxial data cables 30 feature non-parallel wires from the braided shielding layer, crimping of the coaxial data cables becomes challenging and is difficult to automatize.
Figure 2 shows an example manufacturing method according to the present invention. The proposed solution to the manufacturing problems of the state of the art eliminates the braiding step 120. Instead, a parallel extrusion where the insulated core 10 is shielded with a shielding composite and protected with an external jacket 5 in one single production step 140 is proposed. As shielding composite, a matrix 3,4 of a suitable material is co-extruded simultaneously with continuous reinforcement wires 2 and the external jacket 5 (cf. also to fig-ures 3 to 6).
In one configuration, when the matrix 3 of the shielding composite is electro-conductive, an external jacket 5 made of a different material than the matrix 3 can be co-extruded with the shielding composite. In this case the extruder is designed to supply at least three different materials, the continuous wires 2, the material for the matrix 3 and the material for the external jacket 5, simultaneously. Alternatively, the external jacket can also be extruded after the shielding layer has been extruded on the core of conductor wires 1. In any case, it is not necessary to change from an extruder to a braiding machine. In case of several successive extruders, the production speed is not slowed down when compared to a production plant with a braiding machine, as the different extruders all have a similar speed.
In other configurations, the external jacket 5' is made of the same material as the matrix 4. In this case, the matrix 4 is made of non-electroconductive material. The external jacket 5' coextruded with the shielding composite thereby covers the wires with an adapted amount of matrix material to provide for the required protection. Extrusion machines for such coaxial data cables 30, where the matrix material also forms the external jacket 5, are less complex than extrusion machines with a separate external jacket 5, because only one nozzle and one material supply container are needed for the matrix and the external jacket.
Figures 3 to 6 show four different example embodiments of the coaxial data cable 30 according to the invention.
In the data cable 30 of figure 3 a core of conductor wires 1 is surrounded by an insulation layer 6. The shielding layer comprises an electroconductive matrix 3 and a reinforcement of seven continuous wires 2. Between the shielding layer and the core of conductor wires 1 a foil 7 is located. The foil has the function of separating the different elements and it participates in shielding the layer with the shielding composite. Generally, the foil is made of AL PET AL or any metalized foil. The attenuation of the coaxial data cable can be influenced by choosing the matrix material, the material of the continuous wires and the dimensions of the continuous wires. In the present example embodiment, the coaxial data cable 30, with a diameter of 3.8 mm of the continuous wires made of 8xo,16 mm and an electroconductive matrix made of PP and carbon black, can reach an attenuation of about 25 dB. The external jacket 5 can be co-extruded with the shielding layer of matrix and continuous wires.
In contrast, the coaxial data cable of figure 4 does not have an electroconductive matrix but a matrix 4 without electro-conductive properties placed around the core of conductor wires 1 and the insulation layer 6 and embedding the continuous wires 2 to form the shielding layer. The advantage is that the extrusion machine does not need to be as complex as for the production of the coaxial data cable of figure 3. It is not required to add a separate external jacket 5 as the coaxial data cable is already insulated towards the outside with the thicker matrix material forming the external jacket 5'. To obtain an appropriate shielding however, more continuous wires 2 are needed than in the example of figure 3. Furthermore, it can happen that not all the characteristic parameters of usual coaxial cable are reproduced. In this specific case 16 continuous wires 2 have been chosen. The coaxial data cable 30 of figure 4 can reach an attenuation of 65 dB, with a diameter of 0.1 mm of continuous wires made of tin-plated copper. Because the matrix material is not electro-conductive, the choice of the material does not have a significant influence on the attenuation capabilities of the coaxial data cable according to fig. 4.
In the coaxial data cable 30 according to the example of figure 5, a more electro-conductive material has been chosen as matrix 3 for the shielding layer. This could be in particular plastics with the addition of graphene. Consequently, a thicker insulation layer 5 is also required, than the layer of figure 3. Even if this matrix material may be more expensive in some instances, it can be advantageous is some applications where better shielding properties, especially in the high frequency range, and a high attenuation is required, as for example in the medical field or in the field of data security. When choosing a matrix 3 with high electro-conductivity, it is important to equally choose performant continuous wires 2, as the wires have a major influence on the attenuation properties of the coaxial data cable. Preferred materials for the continuous cables in combination with a matrix material of the current example are copper CU, alloy copper CuSn or tinplated copper. In the cable shown in figure 5, 8 continuous wires are arranged symmetrically around the core of conductor wires 1.
Finally, in coaxial data cable 30 of figure 6, a similar attenuation as in the coaxial data cable exemplified in figure 5 is obtained while lowering the rigidity of the coaxial data cable. The same matrix material is used but instead of 8 continuous wires 2, 16 continuous wires having a smaller diameter are placed around the core of conductor wires 1. The cumulated cross-section of the continuous wires of the coaxial data cables of figure 5 and figures 6 are equivalent. The choice of more but thinner cables provide for lower rigidity, which is advantageous when the coaxial data cable is to be installed on a tortuous path, such as often found in automotive applications. The embodiment of figure 6 further has a foil placed between insulation layer 6 and shielding layer.

Claims

Coaxial data cable (30) comprising
- a core of conductor wires (1), and

- a shielding layer arranged around the conductor wires, made of an extruded shielding composite comprising a matrix (3, 4) and a reinforcement by continuous wires (2), the continuous wires (2) preferably extending substantially parallel to each other.
Coaxial data cable (30) according to claim 1, further comprising
- an insulation layer (6) directly surrounding the core of conductor wires, the insulation layer being arranged between the core of conductor wires (1) and the shielding layer, the insulation layer (6) preferably being covered by a foil (7) arranged between insulation layer (6) and shielding layer, and/or

- an external jacket (5, 5') arranged on top of the shielding layer.
Coaxial data cable (30) according to claim 1 or 2, wherein the material of the matrix (3) of the shielding composite is electroconductive, with a conductivity of at least 1*10⁵ S/m, preferably at least 5*10⁵ S/m, more preferably at least 1*10⁶ S/m and most preferably at least 1*10⁷ S/m, wherein the matrix (3) of the shielding composite is made of plastic doped with graphene, carbon black or additives causing electrical conductivity, such as Polypropylene with carbon black, PVC with carbon black, PVC with Graphene.
Coaxial data cable (30) according to claim 1 or 2, wherein the material of the matrix (4) of the shielding composite is not electroconductive, with a conductivity of less than 1*10² S/m, wherein the matrix (4) of the shielding composite is made of PP, TPE-S , PVC.
Coaxial data cable (30) according to any preceding claim, whereby the continuous wires (2) have a diameter of 0,1 mm to 1 mm, preferably between 0,1 mm and 0,8 mm, more preferably between 0,2 mm and 0,6 mm.
Coaxial data cable (30) according to any preceding claim, whereby the continuous wires (2) have a conductivity of at least 1*10⁶ S/m, preferably at least 5*10⁶ S/m, more preferably at least 1*10⁷ S/m and most preferably at least 5*10⁷ S/m, and wherein preferably the conductivity of the continuous wires (2) is higher than the conductivity of the matrix (3, 4).
Coaxial data cable (30) according to claim 6, wherein the continuous wires (2) of the shielding composite are made of copper, alloy copper or tinplated copper.
Coaxial data cable (30) according to any preceding claim, whereby at least 4 continuous wires (2) are arranged symmetrically around the core of conductor wires (1), preferably at least 8 continuous wires (2) are arranged symmetrically around the core of conductor wires (1), more preferably at least 16 continuous wires (2) are arranged symmetrically around the core of conductor wires (1).
Coaxial data cable (30) according to any preceding claim, wherein the diameter of continuous wires (2) is substantially equal the thickness of the shielding layer.
Coaxial data cable (30) according to claims 6 and 8, and claims depending thereupon, where material and/or number and/or diameter of the continuous wires (2) is chosen to provide attenuation of at least 10 dB, more preferably of at least 20 dB.
Coaxial data cable (30) according to any preceding claim, wherein the coaxial data cable is crimped at its ends, for implementation of connection systems like plugs, connectors, hoses or the like.
Coaxial data cable (30) according to any preceding claim, wherein the coaxial data cable does not comprise any layer with intersecting wires, in particular no braided layer, more particularly no braided electromagnetic shielding layer.
Method of producing a coaxial data cable (30) according to any preceding claim, the method comprising
- providing a core of conductor wires (1),

- extruding a shielding layer made of a shielding composite around the core of conductor wires (1), whereby the shielding composite comprises a matrix (3,4) and a reinforcement by continuous wires (2), the continuous wires preferably extending substantially parallel to each other.
Method according to claim 13, wherein the method further comprising at least one of the following steps
- surrounding the core of conductor wires (1) with an insulation layer (6) before extruding the shielding layer, wherein the insulation layer (6) is optionally further surrounded with a foil (7) before extruding the shielding layer,

- extruding an external jacket (5, 5') on top of the shielding layer.
Method according to claim 13 or 14, further including the step of crimping the ends of the coaxial data cable, for implementation of connection systems like plugs, connectors, hoses or the like, whereby the crimping of the coaxial data cable is done in an automatic step.